Calculate the mass of compound (molar mass = `256 g "mol"^(-1)` ) to be dissolved in 75 g of benzene to lower its freezing point by 0.48 K `(K_f = 5.12 K kg "mol"^(-1))`.

Explanation

Apply the formula
`M_2 = (K_f xx w_2 xx 1000)/(Delta T_f xx w_1)`
substituting the values , we have
`256 = (5.12 kg "mol"^(-1) xx wg xx 1000 g kg^(-1) )/(0.48 K xx 75 g)`
` w = (256 xx 0.48 xx 75)/(5.12 xx 1000) g = 1.8 g `